Network virtualization is an important area in data center virtualization and cloud computing. Research in this area has been focusing on performance. Recently, more concerns are placed on the homogeneity between virtual network facilities and existing physical network facilities. Fine-grained control on virtual network is desired. Fine-grained control includes packet filtering. But the more control over packet filtering comes with a price, performance starts to decline with complex packet filtering rules. This is especially true in the cloud computing area. Adoption of public cloud computing services is hampered by a concern with the security of cloud architecture. Cloud service providers seek to have acceptable network protection in their cloud infrastructure. However security dealing with packet filtering generally provides a rich packet filtering capability with compromised performance, or a weak packet filtering capability with ensured high performance.